This invention relates to hydraulically powered shears of the type used in cutting metal plates and sheets and more particularly to means for readily and efficiently adjusting the rake angle or slope of the upper movable shear knife.
The desirability of adjusting the angular disposition of one shear knife relative to the other in a shear is well known and this is customarily accomplished by employing a fixed horizontal lower shear knife and a vertically reciprocable upper shear knife which is angularly adjustable. An example of a rake angle or slope control adjustment for hydraulic shears is found in my prior U.S. Pat. No. 3,129,625 dated Apr. 21, 1964.
In this prior patent the slope adjusting mechanism has direct mechanical engagement with a servo valve which operates to adjust the relative vertical elevations of the operating members of the two hydraulic cylinders which are disposed at opposite sides of the upper portion of the shear for effecting power strokes of the ram and the shear knife carried thereby. This arrangement dictates and requires a construction wherein the rake angle adjusting servo valve is located adjacent to the mechanical means which is manually adjusted to produce desired rake angles and this leaves the rake angle servo valve relatively remote from the other hydraulic controls of the machine, thus requiring conduits of substantial length between the servo valve and the other hydraulic controls of the machine.
Other prior art proposals which seek to locate the rake angle servo valve more conveniently with respect to the other hydraulic controls involve tape or cable connections between the shear frame, the upper movable shear knife or the supporting ram therefore, and the slope adjusting servo valve. While this arrangement accomplishes its intended purpose as outlined above, it requires tape or cable means which extends entirely across the shear from one side to the other.